In my main patent--Italian patent application No. 67392-A/78 entitled Lamp for Motor-Vehicles and filed Feb. 27, 1978--there is described and claimed a lamp for motor vehicles, comprising a base which may be fixed to the body of the motor vehicle, a lamp bulb supported by the base, and a transparent cover fixed to the base to enclose the bulb, the said lamp being characterized by the fact that for the collection of the beam of light emitted by the lamp bulb into a beam having desired photometric characteristics there is provided a transparent prismatic cap interposed between the cover and the bulb.
The advantages deriving from the invention of the main patent are particularly noticeable in those cases, provided for in the patent, in which a cluster of lights (comprising, for example, parking light, stop light, reversing light etc.) constitute an integral part of the profile of the body, rather than a unit in itself, affixed to the body.
The present invention follows from the observation that often, for reasons of design, it is desirable that one or more lights should cover on the outside a relatively extensive area, much greater than that suitable for the said cap. At the same time, it has become desirable that, particularly for a parking light or stop light the said cap should not create (when the light is lit) a spot of extreme luminosity in the middle of the said relatively extensive area. In principle, it should be possible to overcome this difficulty by means of an appropriate "prismatic" configuration of the transparent cap of the lamp; this would, however, mean a return to precisely those problems which the main patent was intended to avoid.